Precision microscope stage

ABSTRACT

The present invention provides a precision stage assembly for an optical microscope which comprises an outer frame adapted to be rigidly mounted on the main structure of an optical microscope, an inner frame for carrying an X and Y traverse device on which a specimen may be carried, an intermediate frame between the inner and outer frames adjustable relative to the outer frame by a coarse focus drive, and releasable clamping means for rigidly clamping together the intermediate and outer frames, said inner frame being adjustable relative to the intermediate frame by a fine focus control mechanism and the inner frame being located with reference to the intermediate frame such that significant relative movement therebetween is restricted to movement in a vertical direction.

nited States Patent George 1 at. 2, 1972 [54] PRECISION MICROSCOPE STAGE2,677,987 5/1954 Gallasch ..350/86 1 Invenrofl Sydney George, Cambridge1511- FOREIGN PATENTS OR APPLICATIONS g an 665,837 7/1964 ltal ..350/84[73] Assignee: Image Analysing Computers Limited, Mely boum Royston,England Primary Examiner-David Schonberg 22 F} d: L 27 1970 AssistantExaminer-Ronald J. Stern 1 l e 0e Atrorney-Beveridge & De Grandi [21]Appl. No.: 84,366

[57] ABSTRACT Foreign Application Priority Data The present inventionprovides a precision stage assembly for an optical microscope whichcomprises an outer frame 1969 Great m "53'406/69 adapted to be rigidlymounted on the main structure of an op- [52] Us Cl 350/86 74/27 269/59tical microscope, an inner frame for carrying an X and Y 350/90 traversedevice on which a specimen may be carried, an inter- [51] Int Cl G02)21/26 mediate frame between the inner and outer frames adjustable [58]Fieid 248/157 relative to the outer frame by a coarse focus drive, and248/419 [137 6 5 59 f releasable clamping means for rigidly clampingtogether the 74/89 l intermediate and outer frames, said inner framebeing adjustable relative to the intermediate frame by a fine focuscontrol [56] References Cited mechanism and the inner frame beinglocated with reference to the intermediate frame such that significantrelative movement' therebetween is restricted to movement in a verticaldirection.

10 Claims, 4 Drawing Figures PATENTEUMAR28 I972 Ill IN V5 NTOR'. DAVIDsvmmy 9550mm PRECISION MICROSCOPE STAGE This invention relates to imageanalysis and in particular to a precision stage for an opticalmicroscope when employed in image analysis.

Due to the restricted field of view of a microscope, only a smallfraction of the total area of a specimen can be seen at any one timewhen viewed through a microscope. In image analysis it is usuallynecessary to consider all or at least a large portion of the total areaof a specimen under analysis and it is thus necessary to movethespecimen relativeto the optical axis of the microscope so that differentregions of the surface of the specimen can be viewed.

A microscope for use in automated image analysis must therefore includeprovision for motorized control of specimen traverse. This traverse maybe incremental along X and Y axes or may be random.

It will be appreciated that it is essential for the specimen to remainin focus during the entire analysis which, when an entire specimen is tobe traversed incrementally along X and Y axes, may take someconsiderable time. Reaction from traverse drive systems andenvironmental disturbances such as operator movement etc., have beenfound to affect the focus setting and it is an object of the presentinvention to provide an image stage for an optical microscope whichallows traverse of a specimen with a significant improvement inresistance to vibration over any previously known microscope stage. I

It is a further object of the present invention to allow for coarse andfine adjustmentof the focus of a specimen on such a stage.

According to the present invention a precision stage assembly for anoptical microscope comprises an outer frame adapted to be rigidlymounted on the main structure of an optical microscope, an innerframefor carrying an X and Y traverse device onwhich a specimen may becarried, an intermediate frame between the inner and outer framesadjustable relative to the outer frame by a coarse focus drive, andreleasable clamping means for rigidly clamping together the intermediateand outer frames, said inner frame being adjustable relative to theintermediate frame by a fine focus control mechanism and the inner framebeing located with reference to the intermediate frame such thatsignificant relative movement therebetween is restricted to movement ina vertical direction.

Preferably the inner frame is located with reference to the intermediateframe by means of a semi-kinematic double plane system ofstrip hinges. 7

Since the movement of the inner frame is restricted to vertical movementrelative to themicroscope body, it is therefore also restricted tomovement in line with the optical axis of the microscope. The designreduces all unwanted movement such as tilt and lateral shift, to aminimum.

Preferably fine focus adjustment is provided by a low-friction leversystem capable of either manual or motorized actuation. The inner frameis at all times restrained between the fine focus lever mechanism andthe intermediate frame.

Conveniently, coarse focus motion is produced by a conventional worm andworm-wheel drive, acting on the intermediate frame to move the latterwith respect to the outer frame and therefore the microscope body.Preferably the coarse focus drive is normally disengaged and is onlyengaged when coarse focusing is required.

According to a particularly preferred feature of the present inventionan interlock is provided between the means for engaging and disengagingthe coarse focus drive, which automatically actuates the clamping meanswhen the coarse focus drive is disengaged. Conveniently the clamping iseffected through two clamping rods, one running along each side of thecombined structure and acting on opposite end walls of the outer frame.

The invention will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. 1 is a perspective view of an optical microscope incorporating aprecision stage constructed as one embodiment of the present invention,

FIG. 2 is a plan view of the stage with parts of the support and outerintermediate frames removed so as to reveal the coarse focus drive andreleasable clamping means,

FIG. 3 is a section III-Ill of FIG. 1 through the stage viewed from thefront and illustrates the fine focus drive, and

FIG. 4 is a further section IVIV of FIG. 1 through the stage as viewedfrom the side and shows another view of the releasable clamping means.

FIG'. 1 illustrates an optical microscope having a base 10, verticalsupport 12 and eyepiece assembly 14. A conventional turret objective 16is also carried by the eyepiece assembly 14.

The microscope stage comprises a three part structure and in accordancewith the invention consists of an outer frame 18, an intermediate frame20 slidable vertically relative to the outer frame 18 and an inner frame22 carrying an X and Y traverse device (not shown) for supporting aspecimen 24. The inner frame 22 is supported within the intermediateframe 20 by means of strip hinges 26 which are shown in greater detailin FIGS. 2 and 3. A control 28 (which is duplicated on theother side ofthe assembly) is provided to effect movement of a coarse focus drive(indicated generally by the reference numeral 37 in FIG. 2) and alsoserves to effect clamping of a releasable clamping mechanism (indicatedgenerally by the reference numeral 49 in FIG. 4).

Referring to FIG. 2, the specimen 24 is here shown mounted in a carriage30 which is itself slidable in a carriage mount 32 located betweenparallel rails 34, 36 on the inner frame 22. The carriage mount 32 isthus capable of sliding movement in one direction only and the carriage30 is capable of sliding movement in a direction perpendicular to thedirection of movement of the carriage mount 32. Appropriate relativemovement of the carriage 30 and carriage mount 32 thus provides for theX and Y traverse required for automated image analysis.

The intermediate frame 20, is slidably mounted relative to the mainmicroscope body and to the outer frame 18 by means of a verticaldovetailed joint of which the recess 38 is carried by the rear wall ofthe intermediate frame 20 and the dovetailed spigot 40 which normallyfits in the dovetailed recess 38 is carried by the vertical rear wall ofthe outer frame 18.

The intermediate frame is moved vertically relative to the outer frameby means of the coarse focusing drive 37. This comprises a worm 42driving a worm-wheel 44 which acts on a vertical screw (not shown)carried by the intermediate frame. Thus rotation of the worm 42 andtherefore the worm-wheel 44 produces vertical displacement of the screw(not shown) and consequent vertical displacement of the intermediateframe 20 relative to the stationary outer frame 18. The worm is driventhrough a dog clutch 45 half of which is formed in the end of the wormand the other half of which comprises the chuck 46. This is keyed to ashaft 48 on which the worm 42 is freely rotatable. A controller 28, 28'is provided at opposite ends of the shaft 48 by which the latter can berotated to effect vertical displacement of the intermediate frame.

The intermediate frame can be clamped rigidly relative to the outerframe by means of the releasable clamping mechanism 49 which is made upfrom two shafts 50, 52 which extend from front to back of the outerframe assembly. At the front end, each shaft 50 is formed with anenlarged head (54, 56 respectively) which engages the front wall of theouter frame members. At its other end, each shaft is pivotally joined toa cam (58, 60 respectively), each said cam including an integral leverportion (61, 62 respectively) engaged by lugs (64 or 66, respectively)mounted rigidly on the shaft 48. The engagement between the lugs andlever arms of the earns 58, 60 is such as to allow rotation of the shaft48 but axial movement of the shaft 48 results in a pivoting of thelever-cam about the pivotal joint between the cam and the respective endof its shaft 50 or 52. It will be seen that the profile of the cam 58 or60 is such that pivoting in either direction will result in a rising camsurface being presented to the rear wall of the outer frame 18 so thatcontinued pivoting of either of the cams will result in its pivotalpoint moving away from the rear surface of the outer frame 18. This canonly be achieved by a compressive action between the outer frame and theintermediate frame so that all abutting surfaces in alignment with eachshaft 50 or 52 become tightly engaged thereby clamping the two framestogether. The natural resilience of the material forming the outer frameallows for the necessary slight movement and the clamping is assisted byfriction material washers 68, 70 on each of the two shafts 50 and 52respectively and located between the front wall of the intermediateframe and the rear surface ofthe front wall of the outer frame.

The clamping mechanism is also shown in FIG. 4 of the drawings whichillustrates in more detail the pivotal joint between the shaft 50 andits cam 58. It will be appreciated that a cross-sectional view showingthe shaft 52 and cam 60 would be similar.

It will be seen from FIG. 4 that the cam is bifurcated so as to lie onopposite sides ofa reduced section end portion 51 of the shaft 50 whichis conveniently formed with parallel sides. A pin or similar joint isprovided between the bifurcated ends of the cam 58 and the reducedsection spigot 51. The lever portion of the cam 60 is formed with athrough bore in which the shaft 48 is freely rotatable but which is ofsmaller diameter than the lugs 64 carried by the shaft 48.

The intermediate frame is partially cut away at 72 (see FIG. 4) toaccommodate vertical displacement of the intermediate frame withoutinterfering with the shaft 50 (and also shaft 52).

Lastly referring to FIG. 3, the inner frame 22 is adjustable in heightrelative to the intermediate frame by means of a fine focus drive 73which is illustrated in some detail in FIG. 3. Operation of the drive isachieved by rotating a knob 74 which can also be seen in FIG. I on thefar side of the perspective view contained therein. The knob 74 iscarried by a shaft 76 having formed thereon two oppositely directedthreads 78, 80. Two L-shaped levers 82, 84 are arranged beneath theinner frame 22 with the arm of lever 82 threadedly engaged on thethreaded portion 78 and the upper arm of L-shaped lever 84 threadedlyengaged on the oppositely handed thread 80. The horizontal limb of eachlever 82, 84 is balanced on a knife edge (86, 88 respectively) and afloating thrust member (90 and 92 respectively) transmits thrust fromthe cantilevered end of the lower limb of the two L-shaped levers (82,84 respectively). The opposite ends of the thrust members 90, 92 engagein appropriate recesses in the under side of the inner frame 22.

The knife edge supports 86, 88 are carried by internal abutments withinthe intermediate frame and in view of this, rotation of the shaft 76 soas to produce movement of the two levers 82, 84 as shown by thearrow-heads (94, 96 respectively) will produce upward displacement ofthe inner frame 22 relative to the intermediate frame 20. This movementis accommodated by the resilience of the strip hinges 26 which it willbe seen from FIG. 3, are arranged in two planes one above the other. Thefour strip hinges in the upper plane, can be seen in FIG. I but the fourstrip hinges in the lower plane are hidden from view in FIG. 1 and onlytwo of these hinges can be seen in the sectional view of FIG. 3.

It will be seen that when the outer and intermediate frames are clampedthere is little risk of relative movement between these two frames andall subsequent significant vertical stage movement is thus confined tothat resulting from the controlled fine focus movement between the innerframe and the intermediate frame. By virtue of the design of the linkagebetween the inner frame and the intermediate frame, a semikinematicdouble plane support system is provided for the inner frame so that allsignificant movement of the inner frame is restricted to verticalmovement between this frame and the intermediate frame and this iscontrolled accurately by the fine focus drive. Also, by virtue of thedesign of this drive, the lack of backlash results in the inner frameremaining fixed vertically at any given focus position.

It will be appreciated that a degree of articulation is required betweeneach of the two arms 82, 84 and the thread engaging member (not shown)associated therewith, to allow the arms to become inclined relative tothe axis of the shaft 76. Conveniently the upper end ofeach arm 82, 84is cut away to form a channel through which the threaded shaft 76 isfree to pass and an internally threaded sleeve (not shown) which engageson the threads 78 or 80, is secured to the upper end of each arm 82 and84 by means of a resilient bridge (not shown). Alternatively theinternally threaded sleeve (not shown) may be pivotally mounted withinan oversize aperture in the upper end of each arm 82, 84 about an axisperpendicular to the shaft 76.

The amount of movement of the inner frame 22 relative to theintermediate frame 22 is governed by the length and the resilience ofthe material forming the strip hinges 26. The arrangement illustrated inthe embodiment described with reference to FIGS. 1 to 4 of theaccompanying drawings allows a limited degree ofmovement of the innerframe 22 sufficient for most purposes. However, where extra movement ofthe inner frame 22 in the vertical direction is required, each striphinge 26 may be formed with a crease or more than one crease forming,for example, an S bend along its length, thereby increasing theeffective length of each strip hinge 26.

I claim:

1. A precision stage assembly for use with an optical microscopecomprising:

an outer frame;

an inner frame for carrying an X and Y traverse device on which aspecimen is carried;

an intermediate frame between the inner and outer frames;

coarse focus control means enabling the intermediate frame to beadjusted relative to said outer frame;

releasable clamping means enabling the intermediate and outer frames tobe rigidly clamped together;

fine focus control means enabling the inner frame to be adjustedrelativeto the intermediate frame; and

means locating the inner frame with reference to the intermediate framein such a manner that significant relative movement therebetween isrestricted to movement in a vertical direction.

2. A precision stage assembly according to claim 1 in which said finefocus control means comprises a low friction lever system locatedbetween said intermediate and inner frames.

3. A precision stage assembly according to claim 2 in which said finefocus control means is actuable manually.

4. A precision stage assembly according to claim 2 in which a motormeans is provided for actuating said fine focus control means.

5. A precision stage assembly according to claim 1 in which said coarsefocus control means comprises a worm and wormwheel drive means acting onsaid intermediate frame for moving the latter with respect to said outerframe.

6. A precision stage assembly according to claim 1 in which a clutchmeans is provided for selectably disengaging said coarse focus controlmeans.

7. A precision stage assembly according to claim 6 further comprising aninterlock means operably located between said clutch means and saidreleasable clamping means such that disengagement of said coarse focuscontrol means results in said outer and intermediate frames becomingclamped together and vice versa.

8. A precision stage assembly according to claim 1 in which saidreleasable clamping means comprises two clamping rods which extend alongtwo opposite sides of the combined structure formed by the outer andintermediate frames and project from opposite ends of said combinedstructure each rod including an enlarged head portion at one end and apivoted cam and integral lever assembly at the other end arranged suchthat pivoting of said cam relative to its rod results in a reduction inthe effective distance between said enlarged head end of the rod andsaid opposed cam surface which produces a compression on the outer andintermediate frame members situated between said enlarged head end ofsaid rod and its opposed cam surface to thereby clamp together saidouter and 10. A precision stage assembly according to claim I whenintermediate frames. combined with an optical microscope having asupporting A precisicn stage assembly according to claim 1 in whichstructure with said outer frame rigidly attached to said supsaid innerframe is located with reference to said intermediate Pomng structureframe by a semi-kinematic double plane system of strip hinges.

1. A precision stage assembly for use with an optical microscopecomprising: an outer frame; an inner frame for carrying an X and Ytraverse device on which a specimen is carried; an intermediate framebetween the inner and outer frames; coarse focus control means enablingthe intermediate frame to be adjusted relative to said outer frame;releasable clamping means enabling the intermediate and outer frames tobe rigidly clamped together; fine focus control means enabling the innerframe to be adjusted relative to the intermediate frame; and meanslocating the inner frame with reference to the intermediate frame inSuch a manner that significant relative movement therebetween isrestricted to movement in a vertical direction.
 2. A precision stageassembly according to claim 1 in which said fine focus control meanscomprises a low friction lever system located between said intermediateand inner frames.
 3. A precision stage assembly according to claim 2 inwhich said fine focus control means is actuable manually.
 4. A precisionstage assembly according to claim 2 in which a motor means is providedfor actuating said fine focus control means.
 5. A precision stageassembly according to claim 1 in which said coarse focus control meanscomprises a worm and worm-wheel drive means acting on said intermediateframe for moving the latter with respect to said outer frame.
 6. Aprecision stage assembly according to claim 1 in which a clutch means isprovided for selectably disengaging said coarse focus control means. 7.A precision stage assembly according to claim 6 further comprising aninterlock means operably located between said clutch means and saidreleasable clamping means such that disengagement of said coarse focuscontrol means results in said outer and intermediate frames becomingclamped together and vice versa.
 8. A precision stage assembly accordingto claim 1 in which said releasable clamping means comprises twoclamping rods which extend along two opposite sides of the combinedstructure formed by the outer and intermediate frames and project fromopposite ends of said combined structure each rod including an enlargedhead portion at one end and a pivoted cam and integral lever assembly atthe other end arranged such that pivoting of said cam relative to itsrod results in a reduction in the effective distance between saidenlarged head end of the rod and said opposed cam surface which producesa compression on the outer and intermediate frame members situatedbetween said enlarged head end of said rod and its opposed cam surfaceto thereby clamp together said outer and intermediate frames.
 9. Aprecision stage assembly according to claim 1 in which said inner frameis located with reference to said intermediate frame by a semi-kinematicdouble plane system of strip hinges.
 10. A precision stage assemblyaccording to claim 1 when combined with an optical microscope having asupporting structure with said outer frame rigidly attached to saidsupporting structure.